One‐stage combined approach en bloc vertebrectomy for primary Ewing's sarcoma of mobile spine in an adult patient: 3 years following aggressive surgery for a rare entity

Key Clinical Message Currently, there is no consensus on the optimal management of nonmetastatic Ewing's sarcoma of the mobile spine. However, associated to chemotherapy, aggressive surgery with en bloc wide resection seems to improve local control and survival. Abstract Primary Ewing's sarcoma (EWS) of non‐sacral spine is extremely rare, especially in middle‐age. Therapeutic strategy aims: to large tumor resection, to provide spine stability and to avoid recurrence through chemo and radiotherapy. We report a case of thoracic spine EWS in an adult treated by combined approach en bloc vertebrectomy.

trauma.Blood tests were normal and the X-ray rechecks after making the diagnosis showed an unobvious suspect image at the level of the right pedicle of the 12th thoracic vertebra (T12) with disappearance of its normal contours (Figure 1A).Magnetic resonance imaging revealed a vascularized mass affecting the right hemivertebral body and posterior arch of T12 with paravertebral soft tissue extension.The spinal cord was mildly compressed (Figure 1B).An extension assessment concluded that it is a primary localization.We performed a computerized tomography guided biopsy and the diagnosis of classical EWS was confirmed by histopathology and immunohistochemistry showing monotonous small round blue cells with minimal amounts of stroma, regular round nuclei and minimal cytoplasm, which were strongly positive to CD99 (Figure 2).Cytogenetic analysis technics were not disposable to evaluate transcript fusion type.
After receiving neoadjuvant chemotherapy based on The EUROpean Ewing tumor Working Initiative of National Groups 1999 (EURO-E.W.I.N.G. 99) protocol including six courses of Vincristine, Ifosfamide, Doxorubicin, and Etoposide (VIDE), a new MRI showed vertebral and paravertebral soft tissue mass regression with longest axial diameters diminution of over 50% (Figure 1C).According to the WBB surgical staging system, sectors included in the axial T12 imaging were 1-6 (part of the body and part of the left posterior arch) and layers of tissue penetration were A to D.
We performed an en bloc vertebrectomy through a double approach surgery: firstly a posterior approach with pedicle screw insertion (two levels above and two levels below), remove of the healthy part of the posterior arch which allow to release the spinal cord from the tumor pseudocapsule, ligation and section of T12 roots (Figure 3A).Secondly a thoraco-phreno-lombotomy to separate the anterior part of the tumor and control the segmental artery.The separation was made by a Gigli saw and the extraction of the vertebra released from all its attachments was possible through a simple rotation of the specimen (Figure 3B,C).Reconstruction was performed with interbody free non-vascularized fibular bone grafting stabilized by the posterior instrumentation.
Histopathological examination of the resected specimen confirmed classical EWS with clear resection margins and good response to chemotherapy with 97% tumor necrosis rate.
Postoperative course was uneventful.After 6 weeks of the surgery, the patient started adjuvant chemotherapy and completed treatment with no evidence of disease on reevaluation at the end of therapy.Three years after surgery, the patient is surviving without neurologic deficit, X-rays revealed consolidation (Figure 4) and with no evidence of recurrence.

| DISCUSSION
EWS remains an enigmatic and particular malignant tumor 100 years after its discovery.Spinal involvement most commonly results from metastasis in advanced stages of the disease, while EWS originating from the spine is rare and extremely rare if the sacrum is excluded.

GHARBI et
Diagnosis could be quite difficult due to an insidious onset, nonspecific symptoms, and misinterpreted images.Thus, symptoms may not be present until neurological deficits occur and diagnosis suspicion may be after several consultations which increase doubts. 7,8The average delay from the onset of symptoms to the diagnosis has been reported to be 34 weeks all locations combined. 9In our case the delay was 48 weeks.That's why approximately 25% of patients present with metastatic disease at diagnosis; fortunately this was not the case of our patient. 3finitive diagnosis requires cytological, immunohistochemical (CD99), and cytogenetic analysis of a pathologic specimen.The translocation involving chromosome 22 is identified in more than 90% of cases, and it is the landmark to differentiate EWS from other small, round blue cell tumors. 3,10urrently, early diagnosis and multimodal treatment combining surgery, chemotherapy, and local radiation therapy increases the chance of a successful outcome. 11ndelicato et al, 12 in a review have reported a five-year survival rate of 71% and local control rate of 89% for nonmetastatic spinal and paraspinal EWS.However, when compared to other sites of occurrence, prognosis of EWS of the spine remains worse. 13nitial chemotherapy and local radiotherapy might be administered before surgery with the aim to shrink bulky and unresectable tumors, to eradicate micrometastases and for acute relief of epidural compression, but it should be noted that there is a variable sensitivity to radiation and chemotherapy due to biological heterogenecity. 1 Although, local radiotherapy had a considerable place in the management of locally extended or unresectable spine EWS especially with epidural compression or with poor chemotherapy response, many authors emphasized the local control superiority of wide surgical resection R0 in patients with good response following induction chemotherapy.In the other hand, safe margins tumor resection, when technically achievable, allows to avoid epidural and local skin and soft tissues potential complications of radiotherapy. 2,11,12n fact, during the last two decades, the outcome in patients with localized disease has improved through an aggressive surgery known as en bloc vertebrectomy by combining anterior and posterior approach or from a single posterior approach as described by Tomita and al. 14 Boriani et al 6 described three major methods of performing en bloc excisions in the thoracolumbar spine: vertebrectomy if the tumor is confined to zones 4-8 or 5-9; sagittal resection when the tumor occupies zones 3-5 or 8-10 and resection of the posterior arch when it is located between the zones 10 and 3 according to their surgical staging system.However, en bloc resection is a highly demanding procedure that must be carefully planned and the greater surgical risk can be accepted only if it offers a safer result and is performed by specialized surgical and anesthesiology teams. 5mong the difficulties to be considered is the release of the spinal cord if the tumor is expanding to layer D according to WBB staging system.In this case theoretical safe margin should include the dura in the resection specimen but the cost-to-benefit ratio of such procedure should be carefully evaluated.Boriani and his collaborators have shown that a simple release of the dura without resection can be accepted and without proven consequence on the risk of recurrence. 6,13ompared to cases where only decompression or lesionectomy was done, patients who underwent en bloc spondylectomy had a lower recurrence rate. 8,15This is why, whenever possible, surgical en bloc wide resection with an anterior column reconstruction is preferable in order to obtain a better oncological control and a better preservation of the spine biomechanics. 2,3,16

| CONCLUSION
Primary EWS of the thoracic spine is an extremely rare tumor.It is a challenging disease not only to treat but also to diagnosis.A high index of suspicion is needed in patients who present with few or nonspecific symptoms.Early diagnosis is essential to obtain better results and improve prognosis.In localized forms of the tumor, multi modal treatment involving neoadjuvant chemotherapy, wide en bloc vertebrectomy with solid reconstruction and

2 , 3 F
I G U R E 1 (A) Standard X-ray (antero-posterior and lateral view) showing a disappearance of normal contours of the right pedicle of T12.(B) MRI (sagittal and axial view) revealing a vascularized mass affecting the right hemivertebral body and posterior arch of T12 with paravertebral soft tissue extension and spinal cord compression.(C) Axial MRI view showing tumor regression after neoadjuvant chemotherapy.

F I G U R E 2
Microscopic examination.Classical Ewing's Sarcoma: Sheets of monotonous small round blue cells with minimal amounts of stroma.Presence of peripheral bone at the top (hematoxylineosin: HEx100).Cartridge: Cellular details with round nuclei and minimal cytoplasm (hematoxylin-eosin: HEx200).F I G U R E 3 (A)Posterior approach with pedicle screw insertion and release of the spinal cord.(B) En bloc vertebrectomy of T12 through the combined approach.(C) Photo and X-ray of T12 after extraction.

F I G U R E 4
Reconstruction of the anterior column by interbody free non-vascularized fibular bone grafting stabilized by the posterior instrumentation: X-ray at 3 years followup showing consolidation without kyphosis.